Paste composition for an electrolytic condenser and electrolytic condenser containing same

ABSTRACT

A paste composition for an electrolytic condenser consisting of electrolyte compounds, ethylene glycol and polyvinyl pyrrolidone. When used as an electrolyte for an electrolytic condenser, the composition furnishes the condenser with good withstand voltage properties and stable electrical properties.

United States Patent Yasukane Kihara Tokyo;

Ushimatsu Morlyama, Fuiisawa-shi; Yolchl Seta, Yokohama-shl, all 01 Japan [72] lnventors [54] PASTE COMPOSITION FOR AN ELECTROLYTIC CONDENSER AND ELECTROLYTIC CONDENSER CONTAINING SAME 2 Claims, 4 Drawing Figs.

[52] U.S. Cl 317/230, 252/622 [51] Int.Cl H0lg9/02 [50] Field of Search 252/622;

[56] References Cited UNITED STATES PATENTS 2,505,180 4/1950 Georgiev et al 252/622 3,067,367 l2/l962 Ross 252/622 X 3,302,071 l/l967 Stahr.... 252/622 X 3,351,823 11/1967 Jenny 262/622 X Primary Examiner-Tobias E. Levow Assistant Examiner-J. Cooper Attorney-Flynn and Frishauf ABSTRACT: A paste composition for an electrolytic condenser consisting of electrolyte compounds, ethylene glycol and polyvinyl pyrrolidone. When used as an electrolyte for an electrolytic condenser, the composition furnishes the condenser with good withstand voltage properties and stable electrical properties.

PASTE COMPOSITION FOR AN ELECTROLYTIC CONDENSER AND ELECTROLYTIC CONDENSER CONTAINING SAME BACKGROUND OF THE INVENTION The present invention relates to a paste composition used as an electrolyte for an electrolytic condenser.

A general paste composition for an electrolytic condenser consists of electrolyte compounds of organic or inorganic acids or salts thereof and solvents for dissolving suid compounds. The typical known solvent is ethylene glycol. However, an electrolytic condenser using such paste as an electrolyte displays insufficient withstand voltage properties due to the low maximum formation voltage obtained by the paste, so that it is barred from use in a circuit impressed with an appreciably high voltage, for example, of 450 volts or higher.

SUMMARY OF THE INVENTION It is accordingly an object of the present invention to provide a paste composition which, when used as an electrolyte for an electrolytic condenser, affords excellent electrical properties to the condenser.

Another object of the invention is to provide a paste composition for an electrolytic condenser capable of improving the withstand voltage strength of said condenser.

Generally, the paste composition of the present invention for an electrolytic condenser consists of electrolyte compounds, ethylene glycol and polyvinyl pyrrolidone. When used as an electrolyte for an electrolytic condenser, the composition has been shown to give the condenser excellent stability and withstand voltage properties.

BRIEF EXPLANATION OF THE DRAWING FIG. 1 is a graph showing the relationship of the proportions of polyvinyl pyrrolidone contained in the paste composition of the present invention for an electrolytic condenser versus the specific resistivity of said composition;

FIG. 2 is a graph indicating changes with time in the voltage in constant voltage formation as compared between the paste composition of the invention and that of the prior art;

FIG. 3 is a graph representing the relationship of the proportions of polyvinyl pyrrolidone contained in the paste composition of the invention versus a breakdown voltage ob-' tained; and

FIG. 4 is a graph denoting changes with time in the voltage in constant current formation as compared between the paste composition according to another embodiment of the invention and that of the prior art.

DETAILED DESCRIPTION OF THE INVENTION Electrolyte compounds used in preparing the paste composition of the present invention for an electrolytic condenser may consist of any one or combination of organic or inorganic acids or salts thereof. Acids capable of preferable use include anhydrous boric acid, benzoic acid, acetic acid, pieric acid, salicylic acid, etc. Typical salts of these acids are ammonium benzoate, ammonium hydrogen succinate, trimethylammonium acetate,-barium picrate, lithium maleate, zinc hydrogen citrate, magnesium phosphate, nickelous nitrate, etc. The paste composition of the present invention for an electrolytic condenser is formed by dissolving the above-listed electrolyte compounds in a mixture of ethylene glycol and polyvinyl pyrrolidone. As compared with the conventional paste composition, it has been found that when used in an electrolytic condenser, the present paste composition is capable of forming a better electrode and furnishes the condenser with greater capacity stability and higher withstand voltage properties when the condenser remains unloaded. It is not clear by what mechanism the polyvinyl pyrrolidone included in the paste composition of the present invention can improve the aforesaid properties thereof. From the fact, however, that the composition containing the polyvinyl pyrrolidone displays a remarkable increase in a maximum formation voltage over the one lacking said polyvinyl pyrrolidone, it is assumed that this material is conductive to the protection or regeneration of the formed surface of the anode of an electrolytic condenser brought in contact with the composition containing said material. The larger the content of polyvinyl pyrrolidone in the paste composition, the more prominent will become the aforementioned effect. While the increased amounts of the polyvinyl pyrrolidone lend to increase the specific resistivity of the composition, such increase ofthe resistivity is not great enough substantially to vary the electrical properties of the condenser. Accordingly, this will not constitute a factor in limiting the proportions of polyvinyl pyrrolidone to be added. It may be generalized that the presence of 4 to 35 percent by weight of polyvinyl pyrrolidone on the basis of the entire composition offers the best electrical and physical properties.

The present invention will be more fully appreciated from the following specific examples.

Example I Samples of tge present inven on Reference samples Anhydrous boric acid (wt. percent) 0. 5 1. 5 6.0 10.0 0.5 1.5 6. 0 10. 0

onium benzoate (wt. percent) Ethylene glycol (wt percent) Polyvinyl pyrrolidone (wt. percent) Brkealfdcwn voltage The breakdown voltages given in the table above are values determined by immersing in 50 ml. each of the four samples of the present paste composition and the four reference samples.

of the other paste composition three aluminum foils 99.99 percent pure, microns thick and 10 cm in area at a space of IS mm. in parallel relationship which had been washed with water, degreased, cleaned with alcohol and allowed to dry, and thereafter carrying out constant current formation at a current density of 100 m./dm.'* with the central foil used as an anode and the foils on both sides thereof as a cathode. Further there were prepared eight different electrolytic condensers in the order of the following steps, using the aforementioned present and reference samples as an electrolyte. The anode of the condenser consisted of an aluminum foil 98 microns thick, 50 mm. X 950 mm. in size, 99.99 percent pure and having a static capacity of 7.9 micro y.f./dm. which, after etching treatment, was formed at constant current in an aqueous solution of ammonium borate until 550 volts were reached. The cathode was formed of another aluminum foil 30 microns thick, 50 X1000 mm. in size and 99.99 percent pure. The anode, cathode and an intermediate layer consisting of a sheet of high-density kraft paperZO microns thick and a sheet of medium-density kraft paper 20 microns thick were rolled together into a cylindrical. form. The cylindrical body dried 1 hour at a pressure of 1 mm. Hg. and a temperature of 80 C. was immersed in the electrolyte 3 hours at a pressure of 20 mm. Hg. and a temperature of 60 C. so as to cause the porous surface of the anode and intermediate layer of the cylindrical body to be impregnated with the electrolyte. After impregnation, the anode and cathode of the cylindrical body were fitted with a terminal, and around the cylindrical body there was wound kraft paper for insulation. Then the cylindrical body was enclosed in a cylindrical aluminum envelope which was closed at one end and had an insulation layer of pitch formed on the inner wall of said closed end portion. The open end of the cylindrical envelope was encapped with a laminate of rubber and synthetic resin in such a manner that the aforementioned terminals projected outside.

The eight different condensers thus prepared were subthe increased content of polyvinyl pyrrolidone is conducive to the rise of a maximum formation voltage.

Example 3 jected to constant current formation at a current density of 5 5 h r were mixed at normal temperature 2.45 parts by m./dm., using a galvanostat. The condensers using the sam- Weight of behloic acid, 180 Parts y Weight of ammonium ples 2 and 3 of the present invention did not display any abbehzoater P y wclght f ethylene glycol and normality when the formation voltage reached 540 v., whereas Pans bywalght of P y y py The 53mph? 9 of the the condenser formed of the reference Sample 2 was 10 present invenrtion thus prepared had a pH of 5.70. By way of prominently delayed in voltage riser after the formation volt- 2252 s folmed z zfi Sample from age stood at l90 v., and started spark discharges when said p y o enzolc parts i welght of volta e increased to 225 v The condenser involving the momum benzoate and 9115 parts by we'ght of ethylene f g I 3 t l t d d It I glycol. The present sample 9 and reference sample 9 displayed creme Samp e wills ex remc d b 220 a specific resistivity of 2860 and 2450 Item. respectively. after the formahoh Vohdgc hmoume to a These two sample paste compositions were formed at constant observed Presem Spark dlschargcs when Sam Voltage w current under the same conditions as in example I, and their 275 v. I formation voltage was determined with the results as shown in Further determination was made of several other electrical Fig 1 his fi the Curve C denotes the present Sample 9 properties of the condensers prepared from the aforesaid samand the curve D the reference sample 9. ples 2 and 3 of the present invention. The results are presented W in the table below. Example 4 3521??? There were prepared in accordance with the recipe given in Stat ic b ised on Di 1 t i Leakage the table below four different samples of a paste composition capaci y t eoretic 0 cc r 0 current of 120 MS. value loss at 500 v according to the present invent on and four different (#L) (percent) (percent) 04a.) reference samples of a paste composition outside of the scope Condenser using of the invention. The present and reference samples were subsample a oi'the 1 3 03 ected to constant current formation under the same condigg f i gqgg 59 2 tions as in example I. The results of determining the breaksample 3ofthe down voltage of each sample are also presented in the table present invention"... 61 18.7 0.03 3.8 below Samples of the present. invention Reference samples Benzoic acid (wt. percent) 1.2 2. 5.0 12.5 1.2 2. 45 5.0 12.5 Ammonium benzoate (wt. percent). 1. 5 2. 8 5.0 10. 5 1. 5 2. 8 5. 0 10. 5 Ethylene glycol (wt. percent) 66.3 69. 75 72.0 73.0 97.3 94. 75 90.0 77.0 Polyvinyl pyrrolidone (wt. percent) 31.0 25.0 18.0 4.0 Breakdown voltage (v.) 515 510 560 475 120 130 150 185 Example 2 Example 5 There were prepared in accordance with the recipe given in 45 the table below dlffefeht l p of 3 Paste composihoh There were prepared in accordance with the recipe shown accordmg to the P f'h one reference Sample in the table below seven different samples of a paste composir p e g a Paste Composlhoh outslde of the scope of the tion according to the present invention and seven different invention. V, 7 7 reference samples representing a paste composition outside of the scope of the invention. Each of the present and reference samples was subjected to constant current formation under samplgs the present R f r the same conditions as in Example 1. The breakdown voltage mventlon ples of these samples is also given in the table below. 5 6 7 8 5 Anhydrous boric acld (wt. porcvnt). 1.5 1.5 1. 5 1. 5 1.5 Ammonium licnzoutn (wt. percent) 2.5 2.5 2.5 2.5 2. 5 Etlliylii uolglycol percent.) ill 86 81 71 tlil hiniii. ..9W1ffi'finiii llfiff. ill 15 25 79 2520 19 n gs nf n i 1 2 .s 4 s n 1 Determination was made of the specific resistivity of the mecmxym compounds samples 5 to 8. The relationship of these values and the pro- (wt. percent): portions of polyvinyl pyrrolidone contained is gi en in Fla 1- fi g lfifigf 12,0 H The sample 8 of the present invention and the reference sam- Acetic acid 4. 2

Trimethylarnmonium ple 5 were Subjected to constant current formation under the acetate same conditions as in Example l and determination was made ggi i f i g of changes with time in formation, voltage. The results are Salicylic neld.

presented in Fig. 2. in this figure, the curve A represents the present sample 8 and the curve B the reference sample 5.

Fig. 3 presents the relationship of the proportions of polyvinyl pyrrolidone contained in the present samples 5 to 8 and the maximum voltages attained. As apparent from the figure,

Lithium nlnntn. Zinc liydro znii cltrutn Magnesium plioiiylphosphate. 0. its Nickelous nltrutc.v 7. ti Ethylene glyc0l.. 76. (l 82. (l 84. 0 81.0 76. il 74. 75 (lit. 15 Polyvinyl pyrrolidono. 4. (l G. 0 8. 4 14. '2 13.6 '24. 0 30. (l Breakdown voltage (v.). 425 435 460 540 460 570 500 IabLe (Lon! i ru ed.

Reference samples Electrolyte compounds (wt. percent):

Ammonium hydrogen suecinate 12.0

Barium picrate. Salicylic acid- As clearly seen from the data of the aforementioned examples, the paste composition of the present invention containing polyvinyl pyrrolidone displays a prominent increase in its breakdown voltage over that lacking said polyvinyl pyrrolidone, regardless of the kind and proportions of the electrolyte compound involved. This means that are electrolytic condenser prepared from this paste composition is also improved in withstand voltage properties.

What is claimed is:

1. In a paste composition for an electrolytic condenser, said composition consisting essentially of ethylene glycol, and at least one compound selected from the group consisting of anhydrous boric acid, bcnzoic acid, acetic acid, picric acid, salicylic acid, ammonium benzoate, ammonium hydrogen succinate, trimethylammonium acetate, barium picratc, lithium maleate, zinc hydrogen citrate, magnesium phenyl phosphate and nickelous nitrate, the improvement comprising the presence of from about 4 to about 35 percent by weight of polyvinyl pyrrolidone in said composition.

2. in an electrolytic condenser containing a pair of aluminum foils electrodes, a porous layer interposed between said electrodes and a paste composition impregnated in said porous layer, a terminal fitted to each of the respective electrodes and an envelope housing the electrodes, porous layer and paste composition, the improvement wherein said paste composition consists essentially of the composition of claim I.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3,609,468 Dated September 28, 1971 I YASUKANE KIHARA et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The Assignee is Tokyo Shibaura Electric Co. Ltd.

Column 2, line 48 "100 m/dm should be 100 mA/dm Column 2, line 55 "micro f/dm should be "micro F/dm Column 3 line 6 "m ./dm should be mA/dm Column 3, line 10 "riser" should be "rise".

Signed and sealed this 10th day of October 1972.

(SEAL) Attest EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

2. In an electrolytic condenser containing a pair of aluminum foils electrodes, a porous layer interposed between said electrodes and a paste composition impregnated in said porous layer, a terminal fitted to each of the respective electrodes and an envelope housing the electrodes, porous layer and paste composition, the improvement wherein said paste composition consists essentially of the composition of claim
 1. 